Huahuan Electronics HX.PTP-GM02, User Manual

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Beijing Huahuan Electronics Co., Ltd
4G/5G base stations, including smallcells, require sub-
µ
s timing
synchronization. When Ethernet becomes the preferred technology for backhaul
transmission, PTP is considered one of the main synchronization techniques. In
principle, the complete backhaul network could constitute a single timing domain.
In such a scheme, a T-GM is placed at the mobile core, and timing is distributed
to every station through the vast expanse of complete set of core, aggregation, and
access networks. This arrangement, however, has two problems.
Problem No.1, it is necessary that every node in the entire carrier’s backbone
packet transport network is PTP ready. The fact is that most of the legacy network
equipment does not support PTP. It will need an enormous capital investment to
replace all the equipment just for synchronization, while they are still quite
capable for all the other functionalities needed for mobile backhaul operations.
When smallcells are concerned, the backhaul may not entirely be owned by the
carrier, part of the transport could be carried by the public internet. It is simply
not practical to upgrade the entire internet to support PTP.
Problem No.2, even if all the nodes support PTP, the end results may not be
adequate if too many intermediate nodes are crossed by the packets, between the
end base station and the T-GM at the core network. This is because each node will
contribute some phase error, causing degradation to the end-to-end clock quality,
while 4G/5G mobile technology requirement for timing accuracy is too stringent
to satisfy. Another drawback is that the added PTP packets to and from every
node in the network dramatically increases the total load of the network
bandwidth.
The more appropriate arrangement is to put a number of T-GM’s at the edge
of the network, closer to the base stations and smallcells. In this way, PTP timing
domains are localized, the rest of the network just provides necessary bandwidth
for data transmission, which most of existing backbone networks and even public
internet are capable of. One of the key requirements for this arrangement is the
availability of high quality, low cost, easy to install GM devices. The
4 HX.PTP-GM02 IEEE-1588 Grandmaster Clock V1.0